Double-String Battery System with Reconfigurable Cell Topology Operated as a Fast Charging Station for Electric Vehicles

This paper introduces a novel design of an electric vehicle (EV) fast charging station, consisting of a battery energy storage system (BESS) with reconfigurable cell topology. The BESS comprises two battery strings that decouple the power flow between EV and grid, to enable charging powers above the...

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Bibliographic Details
Published in:Energies (Basel) 2021-05, Vol.14 (9), p.2414
Main Authors: Engelhardt, Jan, Zepter, Jan Martin, Gabderakhmanova, Tatiana, Rohde, Gunnar, Marinelli, Mattia
Format: Article
Language:English
Subjects:
adaptive cell switching
Aging
battery balancing
battery energy storage system
battery management system
DC-DC converter
Design
electric vehicle
Electric vehicles
Energy conversion efficiency
Energy storage
Immunological tolerance
Infrastructure
Power flow
Reconfiguration
Strings
Topology
Voltage converters (DC to DC)
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Summary:This paper introduces a novel design of an electric vehicle (EV) fast charging station, consisting of a battery energy storage system (BESS) with reconfigurable cell topology. The BESS comprises two battery strings that decouple the power flow between EV and grid, to enable charging powers above the grid capacity. The reconfigurable design is achieved by equipping the battery cells with semiconductor switches and serves two main purposes. First, it aims at solving cell unbalance issues to increase safety, reliability, and lifetime of the battery. Second, it enables the BESS to actively control the EV charging process by changing its cell configuration in a real-time fashion, making a DC-DC converter redundant. The paper presents a modelling approach that captures the reconfigurable design including the controlling algorithm used for cell engagement. The simulation results show that the BESS is able to fulfil the EV request with sufficient accuracy for most of the fast charging process. However, the switching of cells leads to variations in the charging current that can potentially exceed the tolerance band defined in IEC61851-23. Therefore, complementary measures are suggested to achieve a suitable current control during all phases of the charging process. The estimated BESS efficiency during the EV fast charging process is 93.3%. The losses caused by the reconfigurable design amount to 1.2% of the provided energy. It is demonstrated that the proposed design has a competitive efficiency compared to a battery buffered fast charging station with DC-DC converter.
ISSN:1996-1073
1996-1073
DOI:10.3390/en14092414